The invention relates to a method of winding an advancing yarn to form a package, wherein a winding spindle is operated in a normal winding operation with a contact roll lying against the surface of the package being formed, and in an initial winding operation wherein the contact roll is spaced from the surface of the package being formed.
It is known to wind in takeup machines a yarn to a package by driving a winding spindle that receives the package. During a winding cycle, the drive of the winding spindle is controlled in such a manner that the yarn speed remains constant while winding the yarn. To control the rotational speed of the winding spindle, a contact roll lies against the surface of the package during the normal operation. The rotational speed of the contact roll is continuously measured and maintained constant by controlling the rotational speed of the package.
To enable a catching of the yarn on the tube receiving the package, and to prevent damage to the initially wound layers, it is common practice to bring the contact roll into contact with the package surface only after completion of an initial winding phase.
The control of the winding spindle speed is started only after contact is made between the contact roll and the package surface. The startup of this speed control may occur after a predetermined winding time, as disclosed in EP 0 391 101. In this instance, the winding time must be determined such as to ensure that the contact roll and package surface are in contact at that point of time.
EP 0 200 234 discloses a method, which employs for starting up the control a position change of the contact roll that is detected by a sensor. In this method, a position sensing element is used directly for starting up the control.
EP 0 580 548 discloses a method, which employs the change of an operating parameter as a signal for starting up the control. Operating parameters may include the use of the rotational speed of the winding spindle or contact roll, the contact pressure, or the torque of the drives.
In all these methods, the rotational speed of the winding spindle remains uncontrolled during the initial winding operation. As a result of this, a more or less distinctive, sudden change of the winding spindle speed will occur during the transition to the controlled state (normal operation). This change is dependent on the predetermined slope for the speed change of the winding spindle. However, since the circumferential speed of the package is dependent on the yarn deposit, i.e., the diameter increase, a linear change in the rotational speed of the winding spindle results in that the yarn speed cannot be maintained constant during the initial winding operation. This again results in a change of the yarn tension during winding.
It is therefore the object of the invention to provide a method of the initially described type for winding a continuously advancing yarn, wherein the transition from the initial winding operation to the normal winding operation occurs without a significant change in the rotational speed of the winding spindle or the contact roll. A further object of the invention is to provide a method, wherein a package is wound over longer time intervals without controlling the rotational speed of the winding spindle.